There is more to this than just it's the greedy banks again.
Banks are subjected to more government mandated higher regulatory compliance and insurance related compliance costs than credit unions are, all while competing with credit unions for the customers that use the same types of banking services.
Since credit unions do not have to comply with the same regulatory compliance and insurance mandates and pay the costs of complying with those mandates as banks do, credit unions can offer the same types of services to their customers at a lower cost than banks can.